dramatic developments at los angeles international airport. The dry ice bombs bringing to the total to 4 in the last 48 hours. Abc's david wright is at l.A.X. For us this morning. And has the very latest. Good morning, david. Reporter: Good morning, robin. This a major mystery here at l.A.X. A top priority for the lapd and the fbi. The discovery of four, crude, improvised explosive devices. Dry ice bombs, in exstricted areas, parts of the airport where the passengers can't go. Two terminals over two different days. And two of the devices exploded. This morning, los angeles police and the fbi are investigating how four dry ice bombs were placed in restricted areas at the nation's third-busiest airport. One of the homemade devices exploded monday night at 8:20 p.M., Near a gate and close to the planes. No one was injured. Police found two more devices in an area where only employees are allowed and were able to clear them before they detonated. The bottles containing dry ice make for a simple but dangerous explosive device. When the dry ice melts in a bottle, the carbon dioxide gas has nowhere to escape, and explodes, as seen here in a discovery channel special. This comes just a day after a similar incident at l.A.X. On sunday, officials say an airport worker heard an explosion in an employee men's room in terminal two. A 20-ounce plastic bottle was found. That explosion occurred in a restricted area. I think it's crazy. I don't know how things can get in an area where it's not supposed to. Reporter: Officials are combing through the surveillance video, and interviewing witnesses, trying to find out who is leaving these dry ice bombs. We heard there were -- nobody had to evacuate or anything.

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